[llvm] [LV, VP]VP intrinsics support for the Loop Vectorizer + adding new tail-folding mode using EVL. (PR #76172)

[Florian Hahn via llvm-commits]

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@@ -92,7 +92,47 @@ static bool verifyVPBasicBlock(const VPBasicBlock *VPBB,
   for (const VPRecipeBase &R : *VPBB)
     RecipeNumbering[&R] = Cnt++;
 
+  // Set of recipe types along with VPInstruction Opcodes of all EVL-related
+  // recipes that must appear at most once in Entry or Exiting blocks.
+  DenseSet<unsigned> EVLFound;
+  const VPlan *Plan = VPBB->getPlan();
+  bool IsHeader = Plan && Plan->getEntry()->getNumSuccessors() == 1 &&
+                  Plan->getVectorLoopRegion()->getEntry() == VPBB;
+  auto CheckEVLRecipiesInsts = [&](const VPRecipeBase *R) {
+    if (isa<VPEVLBasedIVPHIRecipe>(R)) {
+      if (!IsHeader) {
+        errs() << "EVL PHI recipe not in entry block!\n";
+        return false;
+      }
+      if (!EVLFound.insert(VPDef::VPEVLBasedIVPHISC).second) {
+        errs() << "EVL PHI recipe inserted more than once!\n";
+        return false;
+      }
+      return true;
+    }
+    auto *RInst = dyn_cast<VPInstruction>(R);
+    if (!RInst)
+      return true;
+    switch (RInst->getOpcode()) {
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fhahn wrote:

simpler to use an if for a single case?

https://github.com/llvm/llvm-project/pull/76172